Project Summary Gestational diabetes mellitus (GDM), one of the most common complications of pregnancy affecting about 18% of all pregnancies. GDM is associated with maternal adipose tissue (AT) dysfunction, with increased lipolysis and abnormal production of adipokines, which adversely affects the quality and quantity of lipids transferred to the fetus and its growth. We hypothesize that adrenomedullin (AM) may be involved in the impairment of lipid metabolism in GDM. AM and its receptor components are expressed in AT and AM levels are elevated in obese and high-fat diet fed mice models and in humans with obesity and Type 2 diabetes mellitus. Changes in AM levels and actions in AT could impact lipid metabolism and thus contribute for the altered lipid metabolism in GDM women. Based on novel findings from our preliminary data, we hypothesize that AM has an important role in lipid metabolism during pregnancy and that high glucose- / TNF-?- induced elevations in the expression and function of AM system increases lipolysis and suppresses lipogenesis in AT contributing to the reported overt dyslipidemia in GDM. We will also assess if these changes are fetal sex dependent, and fat depot specific by measuring changes in omental AT (OAT) and subcutaneous AT (SAT). Our specific aims are: Aim 1: Evaluate if expressions of AM and its receptor components in OAT and SAT in GDM patients are elevated and if these elevations are fetal sex dependent and are regulated by glucose and TNF-?. We will measure mRNA and proteins for AM and its receptor components in OAT and SAT from subjects in NGT with male (NGT-M), NGT with female (NGT-F), GDM with male (GDM-M) and GDM with female (GDM-F) fetus and assess if glucose and TNF-? can increase AM system in explants of OAT and SAT from NGT-M and NGT-F. Aim 2: Assess the effects of AM on lipolysis in OAT and SAT. In this aim we will assess if AM increases lipolysis in OAT and SAT explants from NGT-M and NGT-F women and determine the changes in the expression and activation of lipolysis pathway molecules and insulin signaling in these explants. Aim 3: Examine the involvement of AM in adipogenesis in OAT and SAT during normal and GDM pregnancy. We will assess if AM inhibits adipogenesis by interfering with a variety of molecules involved in fatty acid uptake, transport, lipogenesis, insulin signaling and alters transcription factors and adipokines in OAT and SAT. Therefore, we propose that AM is in involved in GDM related dyslipidemia, and blockage of AM actions with AM antagonists may reverse its adverse effects on maternal lipid metabolism in GDM. .